The present invention relates generally to packages for use in microwave ovens, and pertains more particularly to an easily expandable, nontrapping, flexible, microwave package formed of non-extendable material for the popping or puffing of grains and especially popcorn kernels.
To conserve space during shipping and storage, microwave popcorn packages are often folded flat. During popping by use of microwave energy, the popcorn package expands, with the expansion due to the internal pressure of the steam produced by the popping of the popcorn kernels, the pressure of the popped kernels themselves, as well as other factors. An important feature for maximizing the volume of the popped kernels is the ability of the microwave popcorn package to easily expand. Another important factor for maximizing the volume of the popped kernels is that the number of kernels which are actually popped be maximized by insuring that the unpopped kernels are located together on the susceptor with sufficient dwell time to receive sufficient heat energy to result in popping. The shape of the bag plays an important role in the ability of the bag to expand as well as the ability of unpopped kernels to come in contact with each other and the susceptor before and during popping.
One form of conventional popcorn packages is a bag having a rectangular top, a rectangular bottom and pleated sides and with at least one end being sealed together by attaching the top and bottom together such as but not limited to by folding the end of the bag over onto itself. It is a common problem for unpopped kernels to be propelled in the popping process into folds and crevices in the bag and especially those created by the pleats in the sides adjacent to the end(s) of the bag. Such kernels may tend to be captured in such folds and crevices so that they are unable to travel towards the susceptor and are less likely to be popped during microwave cooking.
Additionally, when first placed in the microwave oven, the pleats of the sides of conventional popcorn packages extend at least partially over the charge of popcorn kernels to be popped. Thus, the initial microwave energy has to penetrate several layers of material which forms the bag. As the material is not completely transparent to microwave energy, part of the microwave energy is absorbed by the material which then is generally not available to the charge of popcorn kernels.
Further, conventional rectangular popcorn bags tend to get hung up in the corners of the microwave ovens. This is undesirable for microwave ovens including turntables as the bag will no longer rotate inside of the microwave cavity but is locked in position by the corner. However, even for microwave ovens which are not equipped with turntables, the expansion of the bag and/or the vibration of the bag caused by the popping of the popcorn does not result in moving the bag to the center of the microwave cavity when the bag gets hung up in a corner of the microwave cavity. This is undesirable as cooler spots typically exist in the corners of the microwave cavity and as lack of movement of the bag subjects certain points in the bag to see specific hot spots or electronic nulls.
Thus, a need continues to exist for an improved flexible paper popcorn package which is easily expandable by the dynamics involved in popping the kernels, which is less likely to capture unpopped kernels during the expansion of the package while subjected to microwave energy, and which provides the most consistent and uniform distribution of microwave energy in maximizing the number and volume of popped popcorn.
Surprisingly, the above need and other objectives can be satisfied by providing, in the preferred form, an expandable microwave package in the form of a bag formed by top and bottom walls of flexible, non-extendable material interconnected together adjacent to their round-like shaped outer peripheries so that the top and bottom walls expand into an opposing double domed shape when the popcorn kernels are popped in the microwave oven. In the most preferred form, the top wall includes a peelable closure seal which vents during microwave cooking and which can be physically separated after microwave cooking for ease of access to the popped popcorn and so that the bag clearly functions as a serving bowl. In other preferred aspects of the present invention, the bag is folded about first and second, parallel, fold lines located on opposite sides of a periphery interconnection portion, then folded about a third fold line extending perpendicularly between the first and second fold lines at which time the popcorn kernels are introduced through the periphery interconnection portion which is then sealed, and then folded about a fourth fold line extending parallel to the third fold line, with the folded bag having a conventional, rectangular shape for secondary packaging.